1. Field of the Invention
The invention relates to a torsional vibration damper, and more particularly to a torsional vibration damper which could be easily assembled on the crankshaft with sufficient clamping force to achieve a high quality torsional vibration damper with easy assembling.
2. Description of the Related Art
In general, as a periodical torque acts on the crankshaft of the vehicle engine, a torsional vibration may be generated. The larger the rotating force of crankshaft is, the more the torsional vibration is, and the longer the length of the crankshaft is or the smaller the rigidity of the crankshaft is, the more the torsional vibration is. If the rotation speed of the crankshaft reaches to a certain point, then the torsional vibration may resonate with the proper vibration of the crankshaft itself to incur a serious vibration, which results in a bad ride feeling and damages of the timing gear or crankshaft.
In order to reduce the torsional vibration of the crankshaft, a torsional vibration damper pulley is mounted at the front end of the crankshaft. The torsional vibration damper includes a rubber layer along the periphery of the hub and a pulley is mounted on the outer surface of the rubber layer, so that it could reduce the periodic torsional vibration caused by the eccentric rotation of the crankshaft, and drive the components such as a water pump or an alternator which are connected by belts hung on the pulley.
FIG. 1 and FIG. 2 show the conventional torsional vibration damper. As shown, the conventional vibration damper includes a hub 2 having a central hole 3 in which a crankshaft is coupled and being formed to have a recess opened on one side, a disc 4 extending from the hub 2, a rim 5 being bent and extending from the periphery of the disc 4, a rubber layer 6 of ring shape attached on the outer surface of the rim 5, and a ring member 8 inserted on the outer surface of the rubber layer 6. A pulley is forcedly inserted or welded on the ring member 8. The pulley may be inserted on the ring member 8 or on the rubber layer 6 directly.
A plurality of grip holes 7 are formed on the disc 4 which are gripped by robot arm to move the damper to a desired place in the assembling stage. But the size of the grip hole 7 is relatively small, so the grip means on the robot arm could not be speedily and correctly aligned with the grip hole 7 of the disc 4, and it is not easy to control the robot arm to pick up the damper.
According to the tendency of demanding for weight reduction of car, the light weight torsional vibration damper pulley is also demanded. Accordingly, it has been attempted to make the torsional vibration damper with light weight metal plate instead of heavy iron cast. If the damper is made of pressed metal plate, the thickness of the disc 4 outside the hub 2 becomes thinner. If the disc 4 is thin, the contact area between the grip means of the robot arm and the grip hole 7 may be also small, so the grip means could not firmly grip the damper, or the grip hole 7 may be deformed, so that the damper pulley could not be firmly assembled on the crankshaft, or assembling error may happens. In consideration of the situation, a blind hole cap 9 may be inserted on the grip hole 7 to prevent the deformation of the grip hole 7 and transfer the sufficient clamping force to the disc 4. But the step of inserting the hole cap 9 into the grip hole 7 is rather cumbersome, and the hole cap 9 may drop out from the grip hole 7.